I heard about the new pci express 3.0 slots and there faster, sometime if i dicide to get a card that supports them do to i have a 2.0 slot what's gonna happen like how big is the difference between 2.0 and 3.0 will there be a big difference? My BIOS has a pci express frequncy which is 100MHz currently will this overclock it to work faster maybe 150MHz-200MHz with a 3.0 card make a difference if the card has the same specs besides one is 2.0 and one is 3.0 HAPPY.
PCI-e 3.0 is currently supported on X79. There are Z68 boards that are ready but will require an IB cpu. When Z77 ships it'll be fully compliant.
Today it's not a big deal with the exception of Tahiti's computational aspects which doesn't really effect gaming.
Consider this though, the adoption of PCI-e 2.0 (and it's 40 lanes) was what kept 1366 relevant for as long as it did. 775 did not support it, and it's been history for awhile now. There's no telling what kind of bandwidth cards 2-3 years out will require.
A more immediate concern is SSDs. The next generation will eclipse SATA 6Gb/s bandwidth and until SATA Express is released they'll have to use PCI-e lanes much like the current Revo 3x2 does. If you're limited to 20 lanes at 2.0 speeds then you've effectively limited yourself to a single video card + pci-e bus controller, or 2x gpus. Not both.
Maybe these things don't concern buyers of Z68, but a year from now it might.